The cup-size catch
Coffee makers define a cup as 5 ounces, not 8. A 12-cup brewer therefore makes 60 ounces of coffee, about 7.5 standard mugs, not 12. This single fact causes more weak pots of coffee than any other mistake: people dose for twelve 8 oz cups and brew sixty ounces, or dose for sixty ounces and wonder why twelve mugs taste thin.
Decide which answer you need before measuring. Brewing a full 12-cup pot? Use the coffee-maker numbers. Filling twelve actual 8 oz mugs, for a crowd or a big batch? Use the full-cup numbers. They differ by 60 percent.
Twelve 8 oz cups (full mugs)
Twelve 8 oz cups is 2,839 milliliters of water. At the standard 1:16 drip ratio, divide 2,839 by 16 to get 177.4 grams of coffee. That converts to 23.7 tablespoons, or 1.48 cups of grounds, so call it 177 grams, 24 tablespoons, or 1.5 cups. This is the number for a crowd: twelve real mugs of coffee.
For a stronger pot at 1:15, divide 2,839 by 15 to get 189.3 grams, about 25.2 tablespoons or 1.6 cups of grounds. For a milder pot at 1:17, divide by 17 to get 167 grams, about 22.3 tablespoons or 1.4 cups. The whole strength range spans barely a quarter cup of grounds, which shows how little dose separates strong from weak at this scale.
Twelve coffee-maker cups (5 oz each)
A full 12-cup brew cycle is 60 ounces, or 1,774 milliliters. At 1:16, divide 1,774 by 16 to get 110.9 grams of coffee: 14.8 tablespoons, or 0.92 cups of grounds. Call it 111 grams, 15 tablespoons, or just under 1 cup. If your scoop holds 2 tablespoons, that is 7.5 scoops.
This is the number most bag labels assume when they say 12 cups. If you have been using a full cup of grounds per 12-cup pot and finding it strong, now you know why: a full cup of grounds is 16 tablespoons, slightly more than the 14.8 the ratio calls for. Close, but consistently a touch strong.
Quick table for common batch sizes
At 1:16 with 8 oz cups, using 7.5 grams per tablespoon: 4 cups need 59.1 grams (7.9 tablespoons). 6 cups need 88.7 grams (11.8 tablespoons). 8 cups need 118.3 grams (15.8 tablespoons, 1 cup of grounds). 10 cups need 147.9 grams (19.7 tablespoons). 12 cups need 177.4 grams (23.7 tablespoons, 1.5 cups of grounds).
For 5 oz coffee-maker cups at 1:16: a 4-cup brew needs 36.9 grams (4.9 tablespoons). 8 cups need 73.9 grams (9.9 tablespoons). 10 cups need 92.4 grams (12.3 tablespoons). 12 cups need 110.9 grams (14.8 tablespoons). The coffee ratio calculator converts any batch size to grams, tablespoons, or cups of grounds.
Batch brewing tips
Grind just before brewing, even for a big pot. Pre-ground coffee goes stale in hours once opened, and a 12-cup batch magnifies any staleness. Use a medium grind for drip machines, like granulated sugar. Too fine, and the machine chokes and over-extracts; too coarse, and the water runs through before extracting enough.
Distribute the grounds evenly and level the bed before brewing so water flows through uniformly. If your machine has a thermal carafe, use it: coffee on a hot plate keeps cooking and turns bitter within 30 minutes. A 12-cup batch deserves the same care as a single cup, just scaled up.